1. Field of the Invention
The present invention relates to a stopwatch and a timepiece including a chronograph function.
2. Description of the Related Art
Multifunction timepieces that include pointers for a chronograph, an alarm, or the like in addition to an hour hand, minute hand, second hand, and other such basic timepiece pointers for indicating the standard time are known in conventional practice as mechanical timepieces with a mainspring drive.
In such multifunction timepieces, the seconds chronograph hand (“chronograph” is hereinafter abbreviated as “CG”) disposed in the middle of the dial, for example, is mounted on a second CG wheel concentric with a seconds wheel and pinion, and is continually driven by the seconds wheel and pinion via a reversing mechanism with detachable gears configured from a reversing plate, a reversing ring, a chronograph coupling lever, and the like (for example, Japanese Laid-Open Patent Application No. 11-258367). Also, the oscillation frequency of the balance (number of oscillations per second) for determining the speed of the mechanical timepiece is generally six, eight, or ten oscillations, and is usually six.
However, when the oscillation frequency of the balance is six oscillations, the smallest unit in the chronograph display is ⅙ seconds, but many specifications provide for graduations on the dial that are actually ⅕ seconds, which results in a problem in that the indicating tip of the second CG hand does not line up with the graduations and the chronograph time cannot be accurately measured.
Six, eight, and ten oscillations all have problems in that when the specifications for the oscillation frequency are determined, the minimum measurable units are set, making it impossible to make a more precise measurement. This problem is not limited to mechanical timepieces and also occurs in quartz timepieces. In other words, specifications are determined for the frequency of a motor pulse outputted to the chronograph stepping motor, and the minimum measurable units are thus set.
The speed of a mechanical timepiece is adjusted by intermittently, not continuously, driving a basic timepiece train wheel by means of a balance, a pallet, and an escape wheel and pinion. Specifically, when the pallet that vibrates in a reciprocating rocking movement collides with the escape wheel and pinion from one direction, the movement speed becomes zero for an instant due to the changeover to the other direction, so the basic timepiece train wheel instantaneously stops and is driven intermittently.
However, when the basic timepiece train wheel is intermittently driven so as to stop for an instant in a state wherein the reversing ring of the reversing mechanism is in contact with the reversing plate, the driving of the second CG hand by the seconds wheel and pinion is performed by overcoming static friction every time, which causes a problem in that friction and slipping tend to repeatedly occur between the seconds wheel and pinion and the reversing plate, and friction is induced between the reversing ring and reversing plate.
Also, when driving and stopping are repeated instantaneously in an alternating manner, the basic timepiece train wheel experiences the effects of an impact on the timepiece, and the pointers may be reversed depending on the degree of the impact, and hence move in a nonuniform manner. As a result, when the second CG hand or the like moves and the time is read during heavy activity, the nonuniformity in pointer movement makes the precise values difficult to read.
It will be clear to those skilled in the art from the disclosure of the present invention that an improved multifunction timepiece is necessary because of the above-mentioned considerations. The present invention meets the requirements of these conventional technologies as well as other requirements, which will be apparent to those skilled in the art from the disclosure hereinbelow.